We will use recombinant DNA techniques to identify and study regulatory sites in prokaryotic lambda and eukaryotic genomes (mouse). The structure of the entre locus carrying genes for heavy chain immunoglobulins isolated from mouse DNA will be determined using recombinant techniques. cDNA copies of mRNAs for all 8 mouse heavy chains (mu, delta, gamma 1, gamma 3, gamma 2b, gamma 2a, alpha, and epsilon) cloned into plasmids will be labelled with 32p and used as probe to isolate clones directly from the genomes of mouse and human. Both DNA from germ line and DNA from differentiated tissue will be studied. Both mRNA and genomic clones will be seqenced using the Maxam-Gilbert technique. The sequences of the genomic clones will be compared with messenger RNA sequences and any differences, for example due to introns will be noted. These data should provide an insight into the regulation, and development of the immune system. We will use the H chain probes to analyse expression of immunoglobulins in differentiated B cells. Both terminally differentiated tissues represented by myelomas and earlier states of differentiation represented by lymphomas and viral transformed cell lines will be studied. Particular attention will be paid to cells such as BCL1 which simultaneously produce surface IgM and IgD plus of the same idiotype. These are representative of a majority of early B cells in the spleen and present a major molecular puzzle. We intend to determine in such cells how a single variable region turns out to be associated with two constant regions. To further our understanding of the mechanism by which DNA replication is initiated the initiator protein of bacteriophage lambda (product of gene O) will be isolated. Its interaction with the origin of replication will be determined. The precise startpoints of DNA replication will be identified. We will also study the mechanism whereby lambda regulates the transcription of its late genes. The sequence of the positive regulator protein Q and the promotor it activates will be determined.